In Visual Basic, I have written a compiler which takes BNF 'like'
definitions, which can then parse ASCII text streams and produce a resultant
parse tree. The parse tree is object oriented so can be accessed
recursively. I originally wrote it for analysing flight plan routes for
aircraft.

I just wonder how much interest there would be in something like this?

Here's a very short example of what a definition might look like (without
the VB code of course):